This invention relates to a mechanical structural joint and particularly one for connecting together the ends of long hollow tubes radiating outwardly from the intersecting points, or nodes, of a multiple tube truss network structure and a method of forming such a joint at the nodes of a truss structure.
Thin-wall hollow tubes are highly advantageous as structural members for creating a lightweight truss structure of large dimensions, particularly one intended for an airborne structure. In such a large truss structure the manner of connecting together the ends of angularly arranged tubes intersecting at the nodes of the truss structure creates a problem. It is normally not desirable to weld together the ends of tube members where they intersect at the truss nodes due to destroying the heat treat condition of the tubes, and other assembly problems. Therefore, some type of mechanical joint must be utilized. Many types of mechanical joints are possible and have been used, such as a central joining piece with arms projecting outwardly at the node in the various directions of the individual tubular members of the truss. However, each tubular member must be separately attached to the central piece, usually a solid forging, requiring a large number of fastenings and resulting in an excessively heavy structure which is expensive and complicated to fabricate. Commonly the ends of the tubes to be joined are completely flattened, the solid flattened ends overlapped and bolted together in the manner of U.S. Pat. No. 4,187,034, USSR Pat. No. 594,269 and European Pat. No. 0 023 721. Various fasteners and central joining pieces have been utilized to mechanically fasten together the ends of hollow tubes at a joint in the manner of U.S. Pat. Nos. 1,582,587, 2,912,075, 4,259,821, 4,322,176 and German Patentschrift No. 237,050.